Device for holding tension test bars



July 10, 1945. J. c. CROCKER DEVICE FQR HOLDING TENSION TEST BARS Filed Sept. 3, 1943 MN %N WN m MN S RN m o WN MN INVENTOR John C. Cracker Patented July 10, 1945 Application September 3, 1943, Serial No. 501,122

7 Claims. (Cl. 24-263) This invention relates to a device for holding tension test bars. The device facilitates gripping of the bars is simple and foolproof in use and easy to manufacture and eifectively grips the bars without the necessity of their being threaded. A bar need simply beinserted into the holding device, whereupon the device .grips and holds the bar and no further operation is necessary.

The holding device preferably employs gripping members adapted to engage and grip the' bar and the structure is such that the effect ofthe gripping members is increased as the tension on the bar increases. Also, means are provided for maintaining the gripping members in proper position to receive a bar when no bar is in place in the device and an initial tension is placed on the holding means to insure holding of a bar before tension is applied.

Other details, objects and advantages of the invention will become apparent as the following comprises an enlarged end I having an exof and is coaxial with the cavity, the bore being internally threaded as shown at 9. The piece B ternally threaded portion ll adapted to be threaded into the piece A as shown in Figure 1, and the piece B also comprises the stem 8. The stem 8 is adapted to be suitably mounted in usual manner in a tension testing machine.

Disposed within the cavity 1 is bar holding means shown as being in the form of cooperating gripping members l2 which are adapted to engage and grip the bar as shown in Figure 1. The

- gripping members l2 are externally tapered from description of a present preferred embodiment thereof proceeds.

In the accompanying drawing 1 have shown a present preferred embodiment of the invention, in which Figure 1 is a central longitudinal cross-sectional view through a device for holding tension testbars, showing one end of a test bar being held thereby;

Figure 2 isan end view of the device as viewed from the left in Figure 1, thebar being shown in transverse cross section; and

Figure 3 is a fragmentary view of a tension test bar of the type for which the particular form of holding device disclosed is adapted.

Referring first to the form of tension test bar shown in Figure 3 and for which the particular holding device shown in the drawing is adapted, the bar comprises a body 2 with enlarged ends I. Each end is provided with an annular recess 4, which recess is tapered inwardly toward the end of the bar, as clearly shown in Figure 3, and ter-.

, minates in a shoulder 5. Such a bar is easy to make and requires no threading. I

Referring now to the holding device shown in Figures 1 and 2, such device comprises ahead 8 provided with a cavity I and, generally opposite the cavity, with a stem 8. The head-is made in two pieces. one piece being designated A and the other B. The piece A has in it the cavity I, which cavity is tapered from smaller to larger cross section from its mouth inwardly as clearly shown in Figure 1. Beyond the cavity 1 the piece smaller to larger cross section in the direction from the mouth of the cavity inwardly so that pull onthe bar results in tightening of the holding means in the cavity. 'I'hegripping members are shown as being of segmental construction, each extending about approximately one-third of the periphery of the bar. The gripping members are maintained apart, when no bar is being gripped, by a split spring ring it enterin grooves I4 in the gripping members.

Each of the gripping members has at its inner face means for interengaging with the tension test bar. In the structure shown'each of the gripping members I 2 has an inward projection l5 adapted to enter the recess 4 of the bar as shown in Figure 1 and having a face It adapted when tension is applied to the bar to bear against the shoulder i of the bar. When tension is applied to the bar the bar tends to pull the gripping members" It to the left viewing Figure 1, but the gripping members are held in the head becausertheir rearward portions are of too great diameter to pass out through the openingat the Disposed within the cavity and bearing against the inner ends of the gripping members is an abutment member IT. The abutment member comprises a body portion II and a central hubll terminating in a steam 2 0. The piece B of the head is provided with a central axial bore 2| receiving the stem 20 of the abutment member I1 so that the abutment member is guided for movement generally axially or the head and of the cavityl.

A nut 22 servingpurely as a stop member is threaded-onto the stem 8 as shown in Figur l. r A compression coil spring It bears against the g nut 22 and against a head 24 of a spider 25 contransmittingthe force of A has a bore which in eflect forms an extension the spring 23 to the holding means the stituting thrust means abutment member IT, as will appear. The spider 25 comprises, in addition to the head 24, three legs 28 which are guided within bores 21 in the piece B of the head and the left-hand ends of the legs 26 abut against the body portion l8 of the abutment member II as shown in Figure 1. Each of the legs 26 is threaded into the head 24 at 28.

When no bar is in place in th holding device the spring 23 acting through the spider 25 and the abutment member I1 resiliently presses the holding means, consisting of the gripping members l2, toward the left viewing Figure 1. The split ring l3 limits the inward or radial movement of the gripping members l2 so that the holding device is normally immediately adapted to receive the tension test bar. The bar is introduced into the device simply by pushing one end of the bar in through the opening surrounded by the gripping members l2 until the projections l5 of the gripping members snap into the recess 4 of the bar. When thebar is pushed into the device the gripping members I! are allowed to yield sufliciently to receive the bar by compression of the spring 23. As the bar is pushed into the opening surrounded by the gripping members l2 it moves the gripping members to the right viewing Figure 1 and they in turn move the abutment member H to the right, compressing the spring 23. Then when the projections snap into the recess 4 the spring 23 acting through the spider 25 and the abutment member II maintains the gripping members I2- at their extreme left-hand position relatively to the head viewing Figure 1 to insure properly holding the bar, even before tension is applied.

After completion of a test the portion of the bar being held by the holding device is removed by pushing the gripping members l2 toward the right viewing Figure 1 by any suitable means, as, for example, release ring 29 shown in chain lines in Figure l. Movementof the release ring 29 toward the right causes it to engage the ends of the gripping members l2 and to push them toward the right until they spread apart sufliciently to to release the portion of the bar held thereby. During the releasing operation the spring 23 is compressed just as during the operation of inserting the bar into the holding device.

Thus my device for holding tension test bars is of great utility as it is virtually automatic in 1 operation and requires no fastening step for fastening a test bar in place. The holding device is of rugged yet simple and inexpensive construction and is virtually foolproof in use.

While I have shown and described a present preferred embodimentof the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied within the scope of the following claims.

I claim:

1. A device for holding tension test bars comprising a head having a cavity therein, which cavity is tapered from smaller to larger cross section from its mouth inwardly, bar holding means in said cavity, said bar holding means comprising cooperating gripping members adapted to engage and grip the bar, said gripping members having'at their inner faces means for interen- "gaging with the bar and being externally tapered from smaller to larger cross section in the direction from the mouth of the cavity inwardly whereby pull on the bar results in tightening of the holding means thereon spring means disposed externally of the head for urgi the gripping means towardthe mouth of the cavity in the head, means mounted on the device against which said spring means bears in one direction and means entering the head and disposed in bearing relationship with respect to the gripping means against which said spring means bears in the opposite direction.

2. A device for holding tension test bars comprising a head having a cavity therein, which cavity is tapered from smaller to larger cross section from its mouth inwardly, bar holding means in said cavity, said bar holding means comprising cooperating gripping members adapted to engage and grip the bar, said gripping members being externally tapered from smaller to larger cross section in the direction from the mouth of the cavity inwardly, an abutment member in the cavity bearing against the inner ends of the gripping members, means for guiding the abutment member generally axially of the cavity and spring means acting on the abutment member for ur ing the gripping members outwardly of the cavity. v

3. A device for holding tension test bars comprising a head having a cavitytherein, which cavity is tapered from smaller to larger cross section from its mouth inwardly, bar holding means in said cavity, said bar holding means comprising cooperating gripping members adapted to engage and grip the bar, said gripping members being externally tapered from smaller to larger cross section in the direction from the mouth of the cavity inwardly, an abutment member in the cavity bearing against the inner ends of the ripping members, means for guiding the abutment member relatively to the head, spring means. disposed externally of the head acting'on the abutment member for urging the gripping members outwardly of the cavity and pressure transmitting means operatively interposed between the spring means and the abutment member.

4. A device for holding tension test bars comprising a head having a cavity therein, whichcavity is tapered from smaller to larger cross section from its mouth inwardly, bar holding means in said cavity, said bar holdingmeans comprising cooperating gripping members adapted to engage and grip the bar, said gripping members being externally tapered from smaller to larger cross section in the direction from the mouth of the cavity inwardly, an abutment member in the cavity bearing against the inner ends of the gripping members, the abutment I member having a stem, the head having a bore receiving said stem whereby the abutment member is guided for movement generally axially of the cavity, and spring means acting on the abutment member for urging the gripping members outwardly of the cavity.

5. A device for holding tension test bars com- 1 members being externally tapered from smaller to larger cross section in the direction from the mouth of the cavity inwardly,spring means disposed externally of the head for urging said holding means outwardLv of the cavity and thrust means operatively interposed between the spring means and the holding means, having a portion the spring means bears and a portion entering the head and disposed in thrust relation to the holdin'g means transmitting the force 0! the sprins means to the holding means.

6. A device for holding tension test bars comprising a head having a cavity therein and having a stem generally opposite the cavity, the cavity being tapered from smaller to larger cross section from its mouth inwardly, bar holdin means in the cavity, the bar holding means comprising cooperating gripping members adapted to engage and grip the bar, the gripping members being externally tapered from smaller to larger cross section in the direction from the mouth of the outwardly of the cavity.

tering the head and disposed in thrust relation to the holding means transmitting the force or e the spring means to the holding means 101: urging the holding means outwardly of the cavity.

'1. A device for holding tension test bars-comprising a head having a cavity therein and having a stem generally opposite the cavity, the cavity being tapered from smaller tolarger cross section from its mouth inwardly, the bar holdin means comprising cooperating gripping members adapted to engage and grip the bar, the gripping members being externally tapered from smaller to larger cross section in the direction from the mouth of the cavity inwardly, spring means disposed about the stem and a spider having legs passing through openings in the head for transmitting the force of the spring means to the holding means for urging the holding means JOHII C. CROCKER. 

